Screening of Volatile Compounds, Traditional and Modern Phytotherapy Approaches of Selected Non-Aromatic Medicinal Plants (Lamiaceae, Lamioideae) from Rtanj Mountain, Eastern Serbia

Ironwort (Sideritis montana L.), mountain germander (Teucrium montanum L.), wall germander (Teucrium chamaedrys L.), and horehound (Marrubium peregrinum L.) are species widely distributed across Europe and are also found in North Africa and West Asia. Because of their wide distribution they express significant chemical diversity. For generations, these plants have been used as medical herbs for treating different aliments. The aim of this paper is to analyze volatile compounds of four selected species that belong to the subfamily Lamioideae, family Lamiaceae, and inspect scientifically proven biological activities and potential uses in modern phytotherapy in relation to traditional medicine. Therefore, in this research, we analyze the volatile compounds from this plants, obtained in laboratory by a Clevenger-type apparatus, followed by liquid–liquid extraction with hexane as the solvent. The identification of volatile compounds is conducted by GC-FID and GC-MS. Although these plants are poor in essential oil, the most abundant class of volatile components are mainly sesquiterpenes: germacrene D (22.6%) in ironwort, 7-epi-trans-sesquisabinene hydrate (15.8%) in mountain germander, germacrene D (31.8%) and trans-caryophyllene (19.7%) in wall germander, and trans-caryophyllene (32.4%) and trans-thujone (25.1%) in horehound. Furthermore, many studies show that, in addition to the essential oil, these plants contain phenols, flavonoids, diterpenes and diterpenoids, iridoids and their glycosides, coumarins, terpenes, and sterols, among other active compounds, which affect biological activities. The other goal of this study is to review the literature that describes the traditional use of these plants in folk medicine in regions where they grow spontaneously and compare them with scientifically confirmed activities. Therefore, a bibliographic search is conducted on Science Direct, PubMed, and Google Scholar to gather information related to the topic and recommend potential applications in modern phytotherapy. In conclusion, we can say that selected plants could be used as natural agents for promoting health, as a source of raw material in the food industry, and as supplements, as well as in the pharmaceutical industry for developing plant-based remedies for prevention and treatment of many diseases, especially cancer.


Introduction
Every culture has its own heritage passed down through generations, mostly verbally, which is considered to be tradition [1]. The way of living that encompass this custom Molecules 2023, 28, 4611 2 of 20 persisted since olden times when phytotherapy was one of the main methods for treating people [2]. People had to use what was available in nature throughout the year, regardless of the season. However, the development stage, as well as the conditions during the season, affect the content of bioactive compounds in these medicinal plants. In contemporary studies, the medical potential for most of these plants was confirmed; however, these findings were empirically confirmed by traditional herbalists and healers in the distant past [3].
The Balkan Peninsula, Serbia as well, is inhabited by different nations, and all of them have specific traditions. Nutrition and healing are closely connected to the available resources found in the surrounding nature. Serbian floristic diversity and its ethnobotanical richness is already described [4][5][6][7]. Rtanj Mountain attracts the most attention, especially because of its pyramidal shape, and local people, as well as visitors and tourists, believe in its mystic powers. Rtanj is an isolated mountain in eastern Serbia with a specific ecosystem that is formed on the dominant karst limestone geologic features [7,8]. Its great importance is also indicated by the fact that Rtanj is under governmental protection as a special nature reserve (spread across 4997.17 ha) ("Official Gazette of RS" No. 18/2019).
Traditional harvest of wild medicinal plants is mostly connected to important dates, whether they be dates in regard to the Serbian Orthodox Church or dates connected to important events in nature. The most important day for plant harvesting in Serbia is the Nativity of Saint John the Baptist (7 July according to the Julian calendar and 24 June according to the Gregorian calendar) and it overlaps with the summer solstice. Several customs are tied to that day; however, the most important is that people believe that plants should be collected on that day, which is defined as Biljober (biljo-ber, srb.biljka, noun-plant; srb.brati, verb-picking). Local people believed that plants collected on this day possess magical properties and stronger healing power.
Sideritis montana L., Teucrium montanum L., T. chamaedrys L., and Marrubium peregrinum L. are plants that spontaneously grow in dry meadows and rocky places, such as Rtanj Mt. in eastern Serbia. These plants belong to the Lamiaceae family (Lamioideae subfamily) and are used in traditional medicine in this region. Their aboveground parts (herba) are collected during the flowering stage. In Serbian agro-ecological conditions, it is usually from June to August. S. montana or mountain ironwort (in Serbian "planinskičistac") is usually applied externally for cleaning and healing wounds caused by iron weapons [9]. T. montanum or mountain germander (in Serbian "trava Iva") can be used as tea for digestive complaints such as gallbladder problems, for blood purification, and for healing hemorrhoids [10,11]. T. chamaedrys or wall germander (in Serbian "podubica") is widely used for curing weaknesses and anemia and for wound cleaning [11]. M. peregrinum or horehound (in Serbian "očajnica") is used for regulating the menstrual cycle [7]. However, most of the medicinal uses of these species are limited to folk medicine.
The goal of this research was to examine the composition of volatile components of four species belonging to the family Lamiaceae, subfamily Lamioideae (S. montana, T. montanum, T. chamaedrys, and M. peregrinum). Selected plants are characterized by low or trace essential oil content. However, they are widely used in traditional medicines in the regions where they grow. Therefore, the aim of this investigation was to review the ethnomedicinal knowledge and application of selected plants in Serbian and other traditional medicines.

Sideritis montana
S. montana is a small annual herb with simple or branched upright stems, 20-30 cm tall, covered with thinning long trichomes. Leaves are narrow, ovate-lanceolate with short petiole opposite. Flowers have a yellow corolla, green calyx, and leaf-like bracts, usually with six arranged in verticillasters. After flowering, the corolla becomes red-brown. The flowering period is from May to August [12]. S. montana is native to the Mediterranean region, south-western and Central Asia. Nowadays, it can be found in wide regions such as in the Czech Republic, Germany, Poland, Norway, Sweden, Latvia, Estonia, and Lithuania, where it was introduced from Southern Europe [13]. However, S. montana is considered a rare and endangered species in Bulgaria, in need of measures for conservation [14]. This species grows in dry and poor meadows, pastures, and rocky and sandy areas [12]. In addition, it is dominant in vegetation of dry pastures and karst in the year after a fire [15]. In Serbian flora, it is recorded as S. montana f. montana [12].
In the S. montana from Rtanj, a total of 34 volatile compounds were detected, comprising 96.6%, and the main volatile compound was germacrene D (22.6%) ( Table 1). In

Sideritis montana
S. montana is a small annual herb with simple or branched upright stems, 20-30 cm tall, covered with thinning long trichomes. Leaves are narrow, ovate-lanceolate with short petiole opposite. Flowers have a yellow corolla, green calyx, and leaf-like bracts, usually with six arranged in verticillasters. After flowering, the corolla becomes red-brown. The flowering period is from May to August [12]. S. montana is native to the Mediterranean region, south-western and Central Asia. Nowadays, it can be found in wide regions such as in the Czech Republic, Germany, Poland, Norway, Sweden, Latvia, Estonia, and Lithuania, where it was introduced from Southern Europe [13]. However, S. montana is considered a rare and endangered species in Bulgaria, in need of measures for conservation [14]. This species grows in dry and poor meadows, pastures, and rocky and sandy areas [12]. In addition, it is dominant in vegetation of dry pastures and karst in the year after a fire [15]. In Serbian flora, it is recorded as S. montana f. montana [12].
S. montana is commonly consumed as an herbal tea and it is important in traditional medicine [23]. It is mainly used orally as tea for relieving cough associated with a cold, for reducing fever, against stomach ailments, as an antihysteric, tonic, and stimulant, and is used externally to treat wounds ( Table 2). The scientifically proven activities are antioxidant, antimicrobial, anti-inflammatory, smooth muscle-relaxing, anti-proliferative, and cytotoxic activities [17,[24][25][26][27][28][29]. These results support the traditional use of S. montana for the healing and prevention of many diseases of modern times.  [9] Smooth muscle-relaxing methanol extract [27] Bulgaria: for relief of cough associated with cold ns [33] Antiproliferative (cervical cancer) and cytotoxic (melanoma, breast adenocarcinoma and human colon cancer) ethanol, methanol, hexane and ethyl acetate extracts, essential oil [17,22] Spain: digestive ns/infusion/internally [34] Antiinflammatory methanol extract [28] ns-not specified.

Teucrium montanum
T. montanum is a perennial plant with a strong taproot and a prostrate branched shot, 5-25 cm long. Young branches have short internodes and are covered with short grey hairs. Leaves are linear, with a short petiole, dark green on the face, and covered with white hairs on the reverse side. Flowers are white-yellow, grouped in hemispherical inflorescences at the tops of the branches. The flowering period is from June to August [12]. T. montanum inhabits thermophilic limestone and serpentine rocks, dry mountain meadows, and edges of forests in Southern Europe and West Asia [35]. This species possesses a pronounced phenotype plasticity manifested through morpho-anatomical and chemical diversity [36]. There are several varieties recorded in Serbian flora: var. montanum, var. pernassicum, var. hirsutum, and var. skorpilii, according to differentiation of glandular trichomes [12,37,38].
T. montanum is widely used in traditional medicines in many Balkans countries [51] but predominantly in Bosnia and Herzegovina, Serbia, Montenegro, and Kosovo. It is used for treating a wide range of aliments, such as digestive complaints (abdominal pain, constipation, liver damage and gallstones, spasm relief, for improving appetite, etc.), for immune system strengthening, as a tonic, for blood purification, against respiratory disorders such as tuberculosis, as an antipyretic, and for treating rheumatism and skin problems (Table 4). In some regions (Herzegovina, Kosovo, and Croatia), this plant is consumed as a tea, eaten as a dish, or added to alcoholic beverages (alcoholic beverage with herbs, traditionally called "travarica") [52][53][54][55]. The scientifically proven activities of T. montanum are as follows: antitumor, cytotoxic, antioxidant, and antibacterial activities. According to this review, T. montanum can be regarded as a promising candidate to be a natural plant source of effective biological compounds, as a supplement in the food industry, as well as for therapeutic use [56].

Teucrium chamaedrys
T. chamaedrys is a small shrub with a woody-based root system, and it develops underground stolones. The stem is upright and spreading, 10-30 cm high. Leaves have short petiole, are broad with many rounded lobes and a broad rounded tip similar to common oak (in Serbian "dub" because of leaf similarity with Quercus robur, the common Serbian name for T. chamaedrysis "podubica", i.e., like oak). Pink flowers appear during summer (from June to August) [12]. The plant inhabits rocky limestone areas, dry mountain meadows and pastures, and edges of sparse oak and pine forests up to 1000 m above sea level in Central Europe, the Mediterranean region, and Western Asia [35]. In Serbian flora, it is recorded as var. glanduliferum and var. chamaedrys with two forms: f. chamaedrys and f. viride [12].
T. chamaedrys is one of the most popular traditional remedies in the Balkans, used as tea in everyday nutrition [53], as well as for treating many disorders (Table 6). It is used in Turkey, Serbia, Kosovo, and Bosnia and Herzegovina for gastrointestinal aliments, such as spasm relief, liver, spleen and gall aliments, diarrhea, loss of appetite, stomachache, hemorrhoids, and against ulcers, respiratory ailments including bronchitis, tuberculosis, fever, as well as vaginal infections, kidney pain, chronic inflammation of the mucous membranes in the eyes and nose, toothache, and many others. There are only a few scientifically proven activities of T. chamaedrys: antioxidant, antimicrobial, thyrosinase inhibitory effect, and cytotoxic activities. However, hepatotoxic effects have been reported for T. chamaedrys because this plant contains neoclerodanediterpenes [73]. Therefore, controlled application of this plant is necessary.

Marrubium peregrinum
M. peregrinum is a perennial herbaceous plant. Above-ground parts are gray, densely covered with short hairs and trichomes. Stem is erect, 30-60 cm high, branched in the upper half. The lower leaves are ovate, narrowed at the base into a petiole, while other leaves are elongated to lanceolate and saw-toothed. It has several flowers, usually 6-12 grouped in loose spherical inflorescences. It blooms during July and August. As a typical Pontic-Mediterranean species, it is widespread in Central Europe, the Balkan Peninsula, and Asia Minor. Its habitats are dry pastures, rocky meadows, loams, and sandy soils [12]. It usually grows at low altitudes, generally below 1000 m [81].

Essential Oil Extraction and Analysis
The essential oils were isolated by hydrodistillation from dry above-ground plant parts using a Clevenger-type apparatus using 30.0 g finely ground plant material and 500 mL of water during 2 h. There was a small quantity of extracted essential oils (less than 0.1 mL) in all four samples, so it was additionally applied liquid-liquid extraction with hexane as the solvent.
The GC-FID and GC-MS analysis was performed using an Agilent 7890 gas chromatograph coupled with an Agilent 5975C MSD and flame ionization detector on a

Essential Oil Extraction and Analysis
The essential oils were isolated by hydrodistillation from dry above-ground plant parts using a Clevenger-type apparatus using 30.0 g finely ground plant material and 500 mL of water during 2 h. There was a small quantity of extracted essential oils (less than 0.1 mL) in all four samples, so it was additionally applied liquid-liquid extraction with hexane as the solvent.
The GC-FID and GC-MS analysis was performed using an Agilent 7890 gas chromatograph coupled with an Agilent 5975C MSD and flame ionization detector on a nonpolar HP-5MS fused-silica capillary column Agilent 19091S-433 (conditions were mimicked from Adams [90] and described in detail by Acimovic et al. [91]). The identification of constituents was carried out based on the retention index and by comparison with reference spectra (Wiley 7, NIST 17, and retention-time-locked Adams 4 databases) using the Automated Mass Spectral Deconvolution and Identification System (Amdis 32 ver 2.73) and NIST search ver. 2.3. The relative percentage of the oil constituents was expressed as percentages by FID peak-area normalization.

Data Collection
A bibliographic search on Science Direct, PubMed, and Google Scholar was conducted to collect information about the chemical profiles of volatile components of selected nonaromatic medicinal plants, their traditional applications in folk medicine in Serbia and neighborhood regions (Kosovo, Montenegro, Bosnia and Herzegovina, and Bulgaria) and wider (Spain, Algeria, and Turkey), as well as modern phytotherapy approaches according to bioactivity tests (antioxidant, antimicrobial, anti-inflammatory, antiproliferative and cytotoxic activity, etc.).

Conclusions
Ironwort (Sideritis montana L.), mountain germander (Teucrium montanum L.), wall germander (Teucrium chamaedrys L.), and horehound (Marrubium peregrinum L.) belong to the Lamiaceae family and subfamily Lamioideae. Essential oil content in selected medicinal plants is low (characteristic of the subfamily), but essential oil composition could be useful as an achemotaxonomic marker for the selected location, taking into account the wide range of distribution. In the selected plants from Serbia (Rtanj Mt), the sesquiterpenes were the most abundant class of volatile components: germacrene D (22.6%) in ironwort, trans-sesquisabinene hydrate (15.8%) in mountain germander, germacrene D (31.8%) and trans-caryophyllene (19.7%) in wall germander, and trans-caryophyllene (32.4%) and trans-thujone (25.1%) in horehound. However, these plants contain significant numbers of other bioactive compounds such as phenols, flavonoids, diterpenes and diterpenoids, iridoids and their glycosides, coumarins, terpenes, and sterols, which contribute to their biological potential.
In traditional medicine, ironwort is used to relieve coughs associated with cold coughs, as an antipyretic, for stomach ailments, as a digestive infusion, tonic, and stimulant, as well as an antihysteria and wound-healing agent. Modern phytotherapy reveals that it has antioxidant, antimicrobial, anti-inflammatory, antiproliferative, and cytotoxic effects, as well as the effect of relaxing smooth muscles. In traditional medicine, mountain germander is mainly used for the treatment of digestive problems, strengthening of the immune system, blood purification, antipyretic, respiratory diseases, rheumatism, and skin problems, while modern science shows that it has antioxidant, antibacterial, antitumor, and cytotoxic effects. In traditional medicine, the wall germander is used for digestive problems, respiratory system diseases, heart diseases, and other types of pain and inflammation. However, modern science confirms its antioxidant, antimicrobial, tyrosinase inhibitory, and cytotoxic effects. Traditional Serbian medicine recommends horehound against menstrual problems, anemia, hemorrhoids, and digestive problems, and as a tonic, excitant, reliever, and secretion stimulant, and for the treatment of respiratory tract problems, arrhythmias, and general weakness. However, there are only scientifically confirmed antioxidant and antimicrobial activities for this plant.
Considering the growing popularity of traditional systems of healing, ironwort, mountain germander, wall germander, and horehound could be used as natural agents for promoting health, as well as sources of bioactive compounds for the pharmaceutical and food industries based on traditional knowledge and approved by a modern phytotherapy approach. In addition, sources of raw material could be significant to biological standardization of herbal preparations. Future research should be focused on herbal or polyherbal formulations, investigation of their biological activity, as well as their application in everyday life as commercial products.